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+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/* Functions for reading and writing integers in various endiannesses. */
+
+/*
+ * The classes LittleEndian and BigEndian expose static methods for
+ * reading and writing 16-, 32-, and 64-bit signed and unsigned integers
+ * in their respective endianness. The addresses read from or written
+ * to may be misaligned (although misaligned accesses may incur
+ * architecture-specific performance costs). The naming scheme is:
+ *
+ * {Little,Big}Endian::{read,write}{Uint,Int}<bitsize>
+ *
+ * For instance, LittleEndian::readInt32 will read a 32-bit signed
+ * integer from memory in little endian format. Similarly,
+ * BigEndian::writeUint16 will write a 16-bit unsigned integer to memory
+ * in big-endian format.
+ *
+ * The class NativeEndian exposes methods for conversion of existing
+ * data to and from the native endianness. These methods are intended
+ * for cases where data needs to be transferred, serialized, etc.
+ * swap{To,From}{Little,Big}Endian byteswap a single value if necessary.
+ * Bulk conversion functions are also provided which optimize the
+ * no-conversion-needed case:
+ *
+ * - copyAndSwap{To,From}{Little,Big}Endian;
+ * - swap{To,From}{Little,Big}EndianInPlace.
+ *
+ * The *From* variants are intended to be used for reading data and the
+ * *To* variants for writing data.
+ *
+ * Methods on NativeEndian work with integer data of any type.
+ * Floating-point data is not supported.
+ *
+ * For clarity in networking code, "Network" may be used as a synonym
+ * for "Big" in any of the above methods or class names.
+ *
+ * As an example, reading a file format header whose fields are stored
+ * in big-endian format might look like:
+ *
+ * class ExampleHeader
+ * {
+ * private:
+ * uint32_t mMagic;
+ * uint32_t mLength;
+ * uint32_t mTotalRecords;
+ * uint64_t mChecksum;
+ *
+ * public:
+ * ExampleHeader(const void* data)
+ * {
+ * const uint8_t* ptr = static_cast<const uint8_t*>(data);
+ * mMagic = BigEndian::readUint32(ptr); ptr += sizeof(uint32_t);
+ * mLength = BigEndian::readUint32(ptr); ptr += sizeof(uint32_t);
+ * mTotalRecords = BigEndian::readUint32(ptr); ptr += sizeof(uint32_t);
+ * mChecksum = BigEndian::readUint64(ptr);
+ * }
+ * ...
+ * };
+ */
+
+#ifndef mozilla_EndianUtils_h
+#define mozilla_EndianUtils_h
+
+#include "mozilla/Assertions.h"
+#include "mozilla/Attributes.h"
+#include "mozilla/Compiler.h"
+#include "mozilla/DebugOnly.h"
+
+#include <stdint.h>
+#include <string.h>
+
+#if defined(_MSC_VER)
+# include <stdlib.h>
+# pragma intrinsic(_byteswap_ushort)
+# pragma intrinsic(_byteswap_ulong)
+# pragma intrinsic(_byteswap_uint64)
+#endif
+
+/*
+ * Our supported compilers provide architecture-independent macros for this.
+ * Yes, there are more than two values for __BYTE_ORDER__.
+ */
+#if defined(__BYTE_ORDER__) && defined(__ORDER_LITTLE_ENDIAN__) && \
+ defined(__ORDER_BIG_ENDIAN__)
+# if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
+# define MOZ_LITTLE_ENDIAN() 1
+# define MOZ_BIG_ENDIAN() 0
+# elif __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__
+# define MOZ_LITTLE_ENDIAN() 0
+# define MOZ_BIG_ENDIAN() 1
+# else
+# error "Can't handle mixed-endian architectures"
+# endif
+#else
+# error "Don't know how to determine endianness"
+#endif
+
+#if defined(__clang__)
+# if __has_builtin(__builtin_bswap16)
+# define MOZ_HAVE_BUILTIN_BYTESWAP16 __builtin_bswap16
+# endif
+#elif defined(__GNUC__)
+# define MOZ_HAVE_BUILTIN_BYTESWAP16 __builtin_bswap16
+#elif defined(_MSC_VER)
+# define MOZ_HAVE_BUILTIN_BYTESWAP16 _byteswap_ushort
+#endif
+
+namespace mozilla {
+
+namespace detail {
+
+/*
+ * We need wrappers here because free functions with default template
+ * arguments and/or partial specialization of function templates are not
+ * supported by all the compilers we use.
+ */
+template <typename T, size_t Size = sizeof(T)>
+struct Swapper;
+
+template <typename T>
+struct Swapper<T, 2> {
+ static T swap(T aValue) {
+#if defined(MOZ_HAVE_BUILTIN_BYTESWAP16)
+ return MOZ_HAVE_BUILTIN_BYTESWAP16(aValue);
+#else
+ return T(((aValue & 0x00ff) << 8) | ((aValue & 0xff00) >> 8));
+#endif
+ }
+};
+
+template <typename T>
+struct Swapper<T, 4> {
+ static T swap(T aValue) {
+#if defined(__clang__) || defined(__GNUC__)
+ return T(__builtin_bswap32(aValue));
+#elif defined(_MSC_VER)
+ return T(_byteswap_ulong(aValue));
+#else
+ return T(((aValue & 0x000000ffU) << 24) | ((aValue & 0x0000ff00U) << 8) |
+ ((aValue & 0x00ff0000U) >> 8) | ((aValue & 0xff000000U) >> 24));
+#endif
+ }
+};
+
+template <typename T>
+struct Swapper<T, 8> {
+ static inline T swap(T aValue) {
+#if defined(__clang__) || defined(__GNUC__)
+ return T(__builtin_bswap64(aValue));
+#elif defined(_MSC_VER)
+ return T(_byteswap_uint64(aValue));
+#else
+ return T(((aValue & 0x00000000000000ffULL) << 56) |
+ ((aValue & 0x000000000000ff00ULL) << 40) |
+ ((aValue & 0x0000000000ff0000ULL) << 24) |
+ ((aValue & 0x00000000ff000000ULL) << 8) |
+ ((aValue & 0x000000ff00000000ULL) >> 8) |
+ ((aValue & 0x0000ff0000000000ULL) >> 24) |
+ ((aValue & 0x00ff000000000000ULL) >> 40) |
+ ((aValue & 0xff00000000000000ULL) >> 56));
+#endif
+ }
+};
+
+enum Endianness { Little, Big };
+
+#if MOZ_BIG_ENDIAN()
+# define MOZ_NATIVE_ENDIANNESS detail::Big
+#else
+# define MOZ_NATIVE_ENDIANNESS detail::Little
+#endif
+
+class EndianUtils {
+ /**
+ * Assert that the memory regions [aDest, aDest+aCount) and
+ * [aSrc, aSrc+aCount] do not overlap. aCount is given in bytes.
+ */
+ static void assertNoOverlap(const void* aDest, const void* aSrc,
+ size_t aCount) {
+ DebugOnly<const uint8_t*> byteDestPtr = static_cast<const uint8_t*>(aDest);
+ DebugOnly<const uint8_t*> byteSrcPtr = static_cast<const uint8_t*>(aSrc);
+ MOZ_ASSERT(
+ (byteDestPtr <= byteSrcPtr && byteDestPtr + aCount <= byteSrcPtr) ||
+ (byteSrcPtr <= byteDestPtr && byteSrcPtr + aCount <= byteDestPtr));
+ }
+
+ template <typename T>
+ static void assertAligned(T* aPtr) {
+ MOZ_ASSERT((uintptr_t(aPtr) % sizeof(T)) == 0, "Unaligned pointer!");
+ }
+
+ protected:
+ /**
+ * Return |aValue| converted from SourceEndian encoding to DestEndian
+ * encoding.
+ */
+ template <Endianness SourceEndian, Endianness DestEndian, typename T>
+ static inline T maybeSwap(T aValue) {
+ if (SourceEndian == DestEndian) {
+ return aValue;
+ }
+ return Swapper<T>::swap(aValue);
+ }
+
+ /**
+ * Convert |aCount| elements at |aPtr| from SourceEndian encoding to
+ * DestEndian encoding.
+ */
+ template <Endianness SourceEndian, Endianness DestEndian, typename T>
+ static inline void maybeSwapInPlace(T* aPtr, size_t aCount) {
+ assertAligned(aPtr);
+
+ if (SourceEndian == DestEndian) {
+ return;
+ }
+ for (size_t i = 0; i < aCount; i++) {
+ aPtr[i] = Swapper<T>::swap(aPtr[i]);
+ }
+ }
+
+ /**
+ * Write |aCount| elements to the unaligned address |aDest| in DestEndian
+ * format, using elements found at |aSrc| in SourceEndian format.
+ */
+ template <Endianness SourceEndian, Endianness DestEndian, typename T>
+ static void copyAndSwapTo(void* aDest, const T* aSrc, size_t aCount) {
+ assertNoOverlap(aDest, aSrc, aCount * sizeof(T));
+ assertAligned(aSrc);
+
+ if (SourceEndian == DestEndian) {
+ memcpy(aDest, aSrc, aCount * sizeof(T));
+ return;
+ }
+
+ uint8_t* byteDestPtr = static_cast<uint8_t*>(aDest);
+ for (size_t i = 0; i < aCount; ++i) {
+ union {
+ T mVal;
+ uint8_t mBuffer[sizeof(T)];
+ } u;
+ u.mVal = maybeSwap<SourceEndian, DestEndian>(aSrc[i]);
+ memcpy(byteDestPtr, u.mBuffer, sizeof(T));
+ byteDestPtr += sizeof(T);
+ }
+ }
+
+ /**
+ * Write |aCount| elements to |aDest| in DestEndian format, using elements
+ * found at the unaligned address |aSrc| in SourceEndian format.
+ */
+ template <Endianness SourceEndian, Endianness DestEndian, typename T>
+ static void copyAndSwapFrom(T* aDest, const void* aSrc, size_t aCount) {
+ assertNoOverlap(aDest, aSrc, aCount * sizeof(T));
+ assertAligned(aDest);
+
+ if (SourceEndian == DestEndian) {
+ memcpy(aDest, aSrc, aCount * sizeof(T));
+ return;
+ }
+
+ const uint8_t* byteSrcPtr = static_cast<const uint8_t*>(aSrc);
+ for (size_t i = 0; i < aCount; ++i) {
+ union {
+ T mVal;
+ uint8_t mBuffer[sizeof(T)];
+ } u;
+ memcpy(u.mBuffer, byteSrcPtr, sizeof(T));
+ aDest[i] = maybeSwap<SourceEndian, DestEndian>(u.mVal);
+ byteSrcPtr += sizeof(T);
+ }
+ }
+};
+
+template <Endianness ThisEndian>
+class Endian : private EndianUtils {
+ protected:
+ /** Read a uint16_t in ThisEndian endianness from |aPtr| and return it. */
+ [[nodiscard]] static uint16_t readUint16(const void* aPtr) {
+ return read<uint16_t>(aPtr);
+ }
+
+ /** Read a uint32_t in ThisEndian endianness from |aPtr| and return it. */
+ [[nodiscard]] static uint32_t readUint32(const void* aPtr) {
+ return read<uint32_t>(aPtr);
+ }
+
+ /** Read a uint64_t in ThisEndian endianness from |aPtr| and return it. */
+ [[nodiscard]] static uint64_t readUint64(const void* aPtr) {
+ return read<uint64_t>(aPtr);
+ }
+
+ /** Read a uintptr_t in ThisEndian endianness from |aPtr| and return it. */
+ [[nodiscard]] static uintptr_t readUintptr(const void* aPtr) {
+ return read<uintptr_t>(aPtr);
+ }
+
+ /** Read an int16_t in ThisEndian endianness from |aPtr| and return it. */
+ [[nodiscard]] static int16_t readInt16(const void* aPtr) {
+ return read<int16_t>(aPtr);
+ }
+
+ /** Read an int32_t in ThisEndian endianness from |aPtr| and return it. */
+ [[nodiscard]] static int32_t readInt32(const void* aPtr) {
+ return read<uint32_t>(aPtr);
+ }
+
+ /** Read an int64_t in ThisEndian endianness from |aPtr| and return it. */
+ [[nodiscard]] static int64_t readInt64(const void* aPtr) {
+ return read<int64_t>(aPtr);
+ }
+
+ /** Read an intptr_t in ThisEndian endianness from |aPtr| and return it. */
+ [[nodiscard]] static intptr_t readIntptr(const void* aPtr) {
+ return read<intptr_t>(aPtr);
+ }
+
+ /** Write |aValue| to |aPtr| using ThisEndian endianness. */
+ static void writeUint16(void* aPtr, uint16_t aValue) { write(aPtr, aValue); }
+
+ /** Write |aValue| to |aPtr| using ThisEndian endianness. */
+ static void writeUint32(void* aPtr, uint32_t aValue) { write(aPtr, aValue); }
+
+ /** Write |aValue| to |aPtr| using ThisEndian endianness. */
+ static void writeUint64(void* aPtr, uint64_t aValue) { write(aPtr, aValue); }
+
+ /** Write |aValue| to |aPtr| using ThisEndian endianness. */
+ static void writeUintptr(void* aPtr, uintptr_t aValue) {
+ write(aPtr, aValue);
+ }
+
+ /** Write |aValue| to |aPtr| using ThisEndian endianness. */
+ static void writeInt16(void* aPtr, int16_t aValue) { write(aPtr, aValue); }
+
+ /** Write |aValue| to |aPtr| using ThisEndian endianness. */
+ static void writeInt32(void* aPtr, int32_t aValue) { write(aPtr, aValue); }
+
+ /** Write |aValue| to |aPtr| using ThisEndian endianness. */
+ static void writeInt64(void* aPtr, int64_t aValue) { write(aPtr, aValue); }
+
+ /** Write |aValue| to |aPtr| using ThisEndian endianness. */
+ static void writeIntptr(void* aPtr, intptr_t aValue) { write(aPtr, aValue); }
+
+ /*
+ * Converts a value of type T to little-endian format.
+ *
+ * This function is intended for cases where you have data in your
+ * native-endian format and you need it to appear in little-endian
+ * format for transmission.
+ */
+ template <typename T>
+ [[nodiscard]] static T swapToLittleEndian(T aValue) {
+ return maybeSwap<ThisEndian, Little>(aValue);
+ }
+
+ /*
+ * Copies |aCount| values of type T starting at |aSrc| to |aDest|, converting
+ * them to little-endian format if ThisEndian is Big. |aSrc| as a typed
+ * pointer must be aligned; |aDest| need not be.
+ *
+ * As with memcpy, |aDest| and |aSrc| must not overlap.
+ */
+ template <typename T>
+ static void copyAndSwapToLittleEndian(void* aDest, const T* aSrc,
+ size_t aCount) {
+ copyAndSwapTo<ThisEndian, Little>(aDest, aSrc, aCount);
+ }
+
+ /*
+ * Likewise, but converts values in place.
+ */
+ template <typename T>
+ static void swapToLittleEndianInPlace(T* aPtr, size_t aCount) {
+ maybeSwapInPlace<ThisEndian, Little>(aPtr, aCount);
+ }
+
+ /*
+ * Converts a value of type T to big-endian format.
+ */
+ template <typename T>
+ [[nodiscard]] static T swapToBigEndian(T aValue) {
+ return maybeSwap<ThisEndian, Big>(aValue);
+ }
+
+ /*
+ * Copies |aCount| values of type T starting at |aSrc| to |aDest|, converting
+ * them to big-endian format if ThisEndian is Little. |aSrc| as a typed
+ * pointer must be aligned; |aDest| need not be.
+ *
+ * As with memcpy, |aDest| and |aSrc| must not overlap.
+ */
+ template <typename T>
+ static void copyAndSwapToBigEndian(void* aDest, const T* aSrc,
+ size_t aCount) {
+ copyAndSwapTo<ThisEndian, Big>(aDest, aSrc, aCount);
+ }
+
+ /*
+ * Likewise, but converts values in place.
+ */
+ template <typename T>
+ static void swapToBigEndianInPlace(T* aPtr, size_t aCount) {
+ maybeSwapInPlace<ThisEndian, Big>(aPtr, aCount);
+ }
+
+ /*
+ * Synonyms for the big-endian functions, for better readability
+ * in network code.
+ */
+
+ template <typename T>
+ [[nodiscard]] static T swapToNetworkOrder(T aValue) {
+ return swapToBigEndian(aValue);
+ }
+
+ template <typename T>
+ static void copyAndSwapToNetworkOrder(void* aDest, const T* aSrc,
+ size_t aCount) {
+ copyAndSwapToBigEndian(aDest, aSrc, aCount);
+ }
+
+ template <typename T>
+ static void swapToNetworkOrderInPlace(T* aPtr, size_t aCount) {
+ swapToBigEndianInPlace(aPtr, aCount);
+ }
+
+ /*
+ * Converts a value of type T from little-endian format.
+ */
+ template <typename T>
+ [[nodiscard]] static T swapFromLittleEndian(T aValue) {
+ return maybeSwap<Little, ThisEndian>(aValue);
+ }
+
+ /*
+ * Copies |aCount| values of type T starting at |aSrc| to |aDest|, converting
+ * them to little-endian format if ThisEndian is Big. |aDest| as a typed
+ * pointer must be aligned; |aSrc| need not be.
+ *
+ * As with memcpy, |aDest| and |aSrc| must not overlap.
+ */
+ template <typename T>
+ static void copyAndSwapFromLittleEndian(T* aDest, const void* aSrc,
+ size_t aCount) {
+ copyAndSwapFrom<Little, ThisEndian>(aDest, aSrc, aCount);
+ }
+
+ /*
+ * Likewise, but converts values in place.
+ */
+ template <typename T>
+ static void swapFromLittleEndianInPlace(T* aPtr, size_t aCount) {
+ maybeSwapInPlace<Little, ThisEndian>(aPtr, aCount);
+ }
+
+ /*
+ * Converts a value of type T from big-endian format.
+ */
+ template <typename T>
+ [[nodiscard]] static T swapFromBigEndian(T aValue) {
+ return maybeSwap<Big, ThisEndian>(aValue);
+ }
+
+ /*
+ * Copies |aCount| values of type T starting at |aSrc| to |aDest|, converting
+ * them to big-endian format if ThisEndian is Little. |aDest| as a typed
+ * pointer must be aligned; |aSrc| need not be.
+ *
+ * As with memcpy, |aDest| and |aSrc| must not overlap.
+ */
+ template <typename T>
+ static void copyAndSwapFromBigEndian(T* aDest, const void* aSrc,
+ size_t aCount) {
+ copyAndSwapFrom<Big, ThisEndian>(aDest, aSrc, aCount);
+ }
+
+ /*
+ * Likewise, but converts values in place.
+ */
+ template <typename T>
+ static void swapFromBigEndianInPlace(T* aPtr, size_t aCount) {
+ maybeSwapInPlace<Big, ThisEndian>(aPtr, aCount);
+ }
+
+ /*
+ * Synonyms for the big-endian functions, for better readability
+ * in network code.
+ */
+ template <typename T>
+ [[nodiscard]] static T swapFromNetworkOrder(T aValue) {
+ return swapFromBigEndian(aValue);
+ }
+
+ template <typename T>
+ static void copyAndSwapFromNetworkOrder(T* aDest, const void* aSrc,
+ size_t aCount) {
+ copyAndSwapFromBigEndian(aDest, aSrc, aCount);
+ }
+
+ template <typename T>
+ static void swapFromNetworkOrderInPlace(T* aPtr, size_t aCount) {
+ swapFromBigEndianInPlace(aPtr, aCount);
+ }
+
+ private:
+ /**
+ * Read a value of type T, encoded in endianness ThisEndian from |aPtr|.
+ * Return that value encoded in native endianness.
+ */
+ template <typename T>
+ static T read(const void* aPtr) {
+ union {
+ T mVal;
+ uint8_t mBuffer[sizeof(T)];
+ } u;
+ memcpy(u.mBuffer, aPtr, sizeof(T));
+ return maybeSwap<ThisEndian, MOZ_NATIVE_ENDIANNESS>(u.mVal);
+ }
+
+ /**
+ * Write a value of type T, in native endianness, to |aPtr|, in ThisEndian
+ * endianness.
+ */
+ template <typename T>
+ static void write(void* aPtr, T aValue) {
+ T tmp = maybeSwap<MOZ_NATIVE_ENDIANNESS, ThisEndian>(aValue);
+ memcpy(aPtr, &tmp, sizeof(T));
+ }
+
+ Endian() = delete;
+ Endian(const Endian& aTther) = delete;
+ void operator=(const Endian& aOther) = delete;
+};
+
+template <Endianness ThisEndian>
+class EndianReadWrite : public Endian<ThisEndian> {
+ private:
+ typedef Endian<ThisEndian> super;
+
+ public:
+ using super::readInt16;
+ using super::readInt32;
+ using super::readInt64;
+ using super::readIntptr;
+ using super::readUint16;
+ using super::readUint32;
+ using super::readUint64;
+ using super::readUintptr;
+ using super::writeInt16;
+ using super::writeInt32;
+ using super::writeInt64;
+ using super::writeIntptr;
+ using super::writeUint16;
+ using super::writeUint32;
+ using super::writeUint64;
+ using super::writeUintptr;
+};
+
+} /* namespace detail */
+
+class LittleEndian final : public detail::EndianReadWrite<detail::Little> {};
+
+class BigEndian final : public detail::EndianReadWrite<detail::Big> {};
+
+typedef BigEndian NetworkEndian;
+
+class NativeEndian final : public detail::Endian<MOZ_NATIVE_ENDIANNESS> {
+ private:
+ typedef detail::Endian<MOZ_NATIVE_ENDIANNESS> super;
+
+ public:
+ /*
+ * These functions are intended for cases where you have data in your
+ * native-endian format and you need the data to appear in the appropriate
+ * endianness for transmission, serialization, etc.
+ */
+ using super::copyAndSwapToBigEndian;
+ using super::copyAndSwapToLittleEndian;
+ using super::copyAndSwapToNetworkOrder;
+ using super::swapToBigEndian;
+ using super::swapToBigEndianInPlace;
+ using super::swapToLittleEndian;
+ using super::swapToLittleEndianInPlace;
+ using super::swapToNetworkOrder;
+ using super::swapToNetworkOrderInPlace;
+
+ /*
+ * These functions are intended for cases where you have data in the
+ * given endianness (e.g. reading from disk or a file-format) and you
+ * need the data to appear in native-endian format for processing.
+ */
+ using super::copyAndSwapFromBigEndian;
+ using super::copyAndSwapFromLittleEndian;
+ using super::copyAndSwapFromNetworkOrder;
+ using super::swapFromBigEndian;
+ using super::swapFromBigEndianInPlace;
+ using super::swapFromLittleEndian;
+ using super::swapFromLittleEndianInPlace;
+ using super::swapFromNetworkOrder;
+ using super::swapFromNetworkOrderInPlace;
+};
+
+#undef MOZ_NATIVE_ENDIANNESS
+
+} /* namespace mozilla */
+
+#endif /* mozilla_EndianUtils_h */
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